We prepared ultralow dielectrics with remarkably high mechanical strengths (E similar to 8.1 GPa and H similar to 1.2 GPa). The reactivity of porogens was critical to enhanced mechanical properties of ULK. In the case of non-reactive porogens the mechanical properties of nanoporous ultralow dielectrics dramatically decreased with reduction in dielectric constant. However, reactive CD was very effective in the preparation of ULK for the next generation semiconductors. (C) 2010 Elsevier B. V. All rights reserved.